Sound Science Bite:February 18. What are Little Nucleons
Made Of? (It's not sugar and spice.)

It was reported in the 23 Jan 2015 issue of Science that the
Continuous Electron Beam Accelerator Facility (CEBAF) at Thomas Jefferson
National Accelerator Facility in Newport News, Virginia, is gearing up to find
out what's inside protons and neutrons, the two particles, along with electrons,
that make up all matter the vast majority of us are familiar with. Protons and
neutrons make up the nuclei of atoms, positively charged due to the protons.
Negative electrons "swarm" about the nuclei, forming atoms. The electrons are
responsible for the chemical properties of atoms, which are the basic elements
from hydrogen to carbon to oxygen to ununoctium that combine into molecules
that make up all "ordinary" matter.

You may have learned in school science class that protons and neutrons are
both made up of three quarks: two up quarks and one down quark for the proton,
two down quarks and one up quark for the neutron. These quarks are held together
by the "strong" force (clever name) that is mediated by other particles called
gluons. However, this picture is far too simple. The nucleons are apparently a
mess with so-called "virtual" particles and antiparticles coming into and out
of existence all the time as a result of Heisenberg's Uncertainty Principle
in addition to the original three quarks.

Making the task of figuring out nucleons more difficult is the
apparent fact that you can't isolate a single quark due to the properties of
the strong force. This was satirized by the late physics Nobel Laureate
Mohammad Abdus Salam, who tongue-in-cheek founded the "Quark Liberation Front"
or QLF. CEBAF has been looking at nucleons for years but are now doubling the
energy they use to smash electrons into various targets to see what clues come
out of the debris. The higher the energy, the deeper you can probe into the
nucleons. It will be interesting to see what they come up with.